Image reading device and image forming apparatus

ABSTRACT

This image reading device includes an image sensor module, an environment maintaining portion, and a level correction portion. The image sensor module includes a light emitting portion and a plurality of single-channel light amount sensors. The environment maintaining portion maintains, at a constant state, a light receiving environment for a reference portion forming an end portion, of a single-channel light amount sensor, which corresponds to an end portion of the main scanning region. The level correction portion corrects, each time the image sensor module outputs detection data that corresponds to the main scanning region, a level of the detection data from each of all the single-channel light amount sensors in accordance with a deviation between a level of the detection data regarding the reference portion and a reference level set in advance.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority fromthe corresponding Japanese Patent Application No. 2015-061900 filed onMar. 25, 2015, the entire contents of which are incorporated herein byreference.

BACKGROUND

The present disclosure relates to an image reading device and an imageforming apparatus equipped with the image reading device.

In general, it is known that, in an image reading device, a CIS (contactimage sensor) is employed as an image sensor for reading an image of adocument sheet. In order to improve the speed of reading an image, a CISmodule having a plurality of channels is employed in some cases.

The CIS module having a plurality of channels includes a light emittingportion and a plurality of single-channel light amount sensors. Thelight emitting portion emits light to a main scanning region extendingalong one straight line. The plurality of single-channel light amountsensors are disposed in series along the main scanning region. Each ofthe single-channel light amount sensors receives light from itscorresponding one of partial scanning regions which are each a part ofthe main scanning region, and outputs detection data of the amount ofthe received light. The respective single-channel light amount sensorsperform the receiving of the light and the outputting of the detectiondata in parallel.

It is also known that: the plurality of CISs are disposed along the mainscanning direction with their respective end portions overlapping eachother, and image data outputted by each CIS is corrected on the basis ofa detection result of variation of the amount of light from the lightemitting portion in the CIS. In this case, on the basis of data readfrom a white reference plate opposed to an end portion of each CIS,variation of the amount of light from the light emitting portion isdetected.

SUMMARY

An image reading device according to one aspect of the presentdisclosure includes: an image sensor module, an environment maintainingportion, and a level correction portion. The image sensor moduleincludes a light emitting portion and a plurality of single-channellight amount sensors. The light emitting portion emits light to a mainscanning region extending along one straight line. The single-channellight amount sensors perform in parallel receiving light fromcorresponding partial scanning regions which are each a part of the mainscanning region, and outputting detection data of an amount of thereceived light. The environment maintaining portion maintains, at aconstant state, a light receiving environment for a reference portionforming an end portion of a single-channel light amount sensor whichcorresponds to an end portion of the main scanning region. The levelcorrection portion corrects a level of the detection data from each ofall the single-channel light amount sensors in accordance with adeviation between a level of the detection data regarding the referenceportion and a reference level set in advance. The level correctionportion corrects the level of the detection data each time the imagesensor module outputs the detection data that corresponds to the mainscanning region.

An image forming apparatus according to another aspect of the presentdisclosure includes the image reading device according to the one aspectof the present disclosure and an image forming portion. The imageforming portion forms, on a recording medium, an image that correspondsto the detection data having been corrected, the detection data beingobtained by the image reading device.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription with reference where appropriate to the accompanyingdrawings. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of an image forming apparatus thatincludes an image reading device according to an embodiment of thepresent disclosure.

FIG. 2 is a configuration diagram of an image sensor and a peripherythereof in the image reading device according to the embodiment of thepresent disclosure.

FIG. 3 is a schematic plan view showing the inside of the image sensorin the image reading device according to the embodiment of the presentdisclosure.

FIG. 4 is a block diagram of control-related devices in the imageforming apparatus including the image reading device according to theembodiment of the present disclosure.

FIG. 5 is a time chart of data regarding the image sensor in the imagereading device according to the embodiment of the present disclosure.

FIG. 6 is a block diagram of an image processing portion in the imagereading device according to the embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure will be describedwith reference to the attached drawings. It should be noted that thefollowing embodiment is one example embodying the present disclosure,and, by nature, does not limit the technical scope of the presentdisclosure.

[Configuration of Apparatus]

First, an image reading device 1 and an image forming apparatus 10including the image reading device 1 according to the present embodimentwill be described with reference to FIGS. 1 to 4. The image formingapparatus 10 includes a body portion 2 and the image reading device 1.The image forming apparatus 10 also includes: an operation displayportion 80; and a control portion 8 which controls devices of the bodyportion 2 and the image reading device 1.

For example, the image forming apparatus 10 is a copier, a printer or afacsimile having the function of a copier, a multifunction peripheralhaving a plurality of image processing functions including an imagereading function, or the like.

<Image Reading Device 1>

As shown in FIG. 1, the image reading device 1 includes a document sheetscanning unit 11 and a document sheet table cover 12. The document sheettable cover 12 is supported so as to be rotatable relative to thedocument sheet scanning unit 11. The document sheet scanning unit 11includes a transparent document sheet table 16, and the document sheettable cover 12 is rotatable between a closed position at which thedocument sheet table cover 12 covers the document sheet table 16 and anopen position at which the document sheet table 16 is exposed.

The document sheet table 16 is a portion where a document sheet 90 fromwhich an image is to be read is placed. In general, the document sheettable 16 is referred to as a platen glass.

The document sheet scanning unit 11 further includes a first imagesensor 13 a, a scanning mechanism 110, and the like. In the descriptionbelow, one horizontal direction and its corresponding horizontaldirection orthogonal thereto will be referred to as a main scanningdirection D1 and a sub scanning direction D2, respectively.

The first image sensor 13 a reads an image that corresponds to one linealong the main scanning direction D1 in the document sheet 90, andoutputs image data that corresponds to the read image. The scanningmechanism 110 causes the first image sensor 13 a to shuttle along thesub scanning direction D2 at a position close to the document sheettable 16.

By moving along the sub scanning direction D2, the first image sensor 13a reads an image of the lower surface of the document sheet 90 placed onthe document sheet table 16, and outputs image data that corresponds tothe read image.

The document sheet table cover 12 has an ADF 120 incorporated therein.The ADF 120 includes a document sheet supply tray 121, a document sheetsending-out mechanism 122, a document sheet conveying mechanism 123, anda document sheet discharge tray 124. The document sheet sending-outmechanism 122 sends out one by one, to a document sheet conveying pathR0, document sheets 90 set on the document sheet supply tray 121.

The document sheet conveying path R0 is formed along a predeterminedroute which passes a first position P1 extending along a first contactportion 16 a being a part of the document sheet table 16, and a secondposition P2 in the document sheet table cover 12.

A transparent second contact portion 16 b is fixed so as to extend alongthe second position P2. The scanning mechanism 110 can hold the firstimage sensor 13 a at a position opposed to the first position P1. Thefirst image sensor 13 a is held in a state of being opposed to the firstposition P1 via the transparent first contact portion 16 a.

The document sheet conveying mechanism 123 conveys the document sheet 90sent out from the document sheet sending-out mechanism 122, along thedocument sheet conveying path R0, and discharges the document onto thedocument sheet discharge tray 124. The document sheet conveyingmechanism 123 includes: a roller pair which rotates while nipping thedocument sheet 90 therebetween; a motor which drives one roller of theroller pair to rotate; and the like. The document sheet conveyingmechanism 123 is one example of a document sheet conveying portion.

The main scanning direction D1 is a direction orthogonal to theconveyance direction of the document sheet 90 in the document sheetconveying path R0. In the description below, the upstream side and thedownstream side in the conveyance direction of the document sheet 90 inthe document sheet conveying path R0 will be simply referred to as theconveyance upstream side and the conveyance downstream side,respectively.

In the example shown in FIGS. 1 and 2, the first position P1 is on theconveyance downstream side relative to the second position P2 in thedocument sheet conveying path R0. In other words, the second position P2is on the conveyance upstream side relative to the first position P1.However, it is also conceivable that the second position P2 is on thedownstream side of the document sheet relative to the first position P1.

The ADF 120 operates in a state where the document sheet table cover 12is present at the closed position and the first image sensor 13 a isopposed to the first position P1.

In addition, a second image sensor 13 b is provided in the documentsheet table cover 12. The second image sensor 13 b is fixed at aposition opposed to the second position P2 in the document sheetconveying path R0. The second image sensor 13 b is fixed in a state ofbeing opposed to the second position P2 via the transparent secondcontact portion 16 b.

The first image sensor 13 a reads an image on a first surface of thedocument sheet 90 being moved at the first position P1, and outputsimage data that corresponds to the read image. On the other hand, thesecond image sensor 13 b reads an image on a second surface of thedocument sheet 90 being moved at the second position P2, and outputsimage data that corresponds to the read image. The second surface is thesurface on the opposite side of the first surface.

In the present embodiment, each of the first image sensor 13 a and thesecond image sensor 13 b is a CIS module having a plurality of channels.In the description below, the first image sensor 13 a and the secondimage sensor 13 b are collectively referred to as an image sensor 13.The image sensor 13 is one example of an image sensor module having aplurality of channels. It is conceivable that the image sensor 13 isformed by one image sensor module having a length of the entire imagereading range in the main scanning direction D1. It is also conceivablethat the image sensor 13 is formed by a plurality of image sensormodules which are each shorter than the length of the entire imagereading range and which are disposed along the main scanning directionD1.

As shown in FIGS. 2 and 3, the image sensor 13 includes a plurality oflight emitting portions 131, a lens 132 and a light amount sensor 133.The plurality of light emitting portions 131, the lens 132, and thelight amount sensor 133 are each formed so as to extend along the mainscanning direction D1.

The light emitting portions 131 include a red light emitting portion131R, a green light emitting portion 131G, and a blue light emittingportion 131B. The light emitting portions 131 and the lens 132 are eachformed in a bar shape that extends along the main scanning direction D1.The red light emitting portion 131R, the green light emitting portion131G, and the blue light emitting portion 131B have different emittedlight colors, respectively, and can emit light individually.

Each light emitting portion 131 emits light to a main scanning region A0extending along one straight line. The main scanning region A0 is aregion that extends along the main scanning direction D1.

The light amount sensor 133 receives light from the main scanning regionA0 and outputs detection data of the amount of the received light. Thedetection data is data representing the amount of the received light,and also is data representing the density of the image in the mainscanning region A0.

That is, in the case where the detection data is data that has a greatervalue in accordance with increase in the amount of the received light,the detection data indicates that the smaller the value is, the higherthe density of the image in the main scanning region A0 is. Hereinafter,the detection data directly outputted from the light amount sensor 133will be referred to as primary image data Ia. The primary image data Iais analog data.

For the first image sensor 13 a located at the first position P1, themain scanning region A0 is a region on the first surface of the documentsheet 90 being moved along the document sheet conveying path R0. For thesecond image sensor 13 b, the main scanning region A0 is a region on thesecond surface of the document sheet 90 being moved along the documentsheet conveying path R0. For the first image sensor 13 a being moved bythe scanning mechanism 110, the main scanning region A0 is a region onthe lower surface of the document sheet 90 placed on the document sheettable 16.

For example, it is conceivable that each light emitting portion 131 isan LED array that includes a plurality of light emitting diodes disposedalong the main scanning direction D1. It is also conceivable that eachlight emitting portion 131 includes: one or a plurality of lightsources; and an optical system such as a light guide body and acylindrical lens which converts light emitted from the light source intosheet-like light.

The light amount sensor 133 includes a plurality of single-channel lightamount sensors 1331, 1332, and 1333 disposed in series along the mainscanning direction D1. Each of the single-channel light amount sensors1331, 1332, and 1333 receives light from its corresponding one ofpartial scanning regions A01, A02, and A03 each being a part of the mainscanning region A0, and outputs detection data of the amount of thereceived light. The plurality of single-channel light amount sensors1331, 1332, and 1333 perform the process from the receiving of the lightto the outputting of the detection data in parallel.

The partial scanning regions A01, A02, and A03 are regions obtained bydividing the main scanning region A0 into a plurality of sections. Inthe example shown in FIG. 3, the light amount sensor 133 includes threesingle-channel light amount sensors 1331, 1332, and 1333. Each of thesingle-channel light amount sensors 1331, 1332, and 1333 receives lightfrom its corresponding one of the three partial scanning regions A01,A02, and A03 in the main scanning region A0, and outputs detection dataof the amount of the received light. It is also conceivable that thelight amount sensor 133 includes two, four, or more of thesingle-channel light amount sensors.

Each single-channel light amount sensor 1331, 1332, 1333 outputscorresponding primary image partial data Ia1, Ia2, Ia3 each being a partof the primary image data Ia, as detection data of the amount of thereceived light. Each primary image partial data Ia1, Ia2, Ia3 is a datarow regarding a plurality of pixels in its corresponding partialscanning region A01, A02, A03.

Each single-channel light amount sensor 1331, 1332, 1333 includes aplurality of photoelectric conversion elements disposed along the mainscanning direction D1. In general, the photoelectric conversion elementsare CMOS image sensors. Each photoelectric conversion element in eachsingle-channel light amount sensor 1331, 1332, 1333 detects the amountof light emitted from its corresponding pixel in the main scanningregion A0. That is, the photoelectric conversion elements correspond tothe plurality of pixels, respectively. Each single-channel light amountsensor 1331, 1332, 1333 outputs detection data of the light amount ofits corresponding pixels, as the primary image partial data Ia1, Ia2,Ia3.

In the description below, the first contact portion 16 a opposed to thefirst image sensor 13 a located at the first position P1, the secondcontact portion 16 b opposed to the second image sensor 13 b, and apart, of the document sheet table 16, that is opposed to the first imagesensor 13 a being moved by the scanning mechanism 110 will becollectively referred to as a contact portion 160.

As shown in FIG. 2, the light emitting portion 131 of the image sensor13 emits light through the contact portion 160 to the main scanningregion A0 including a part of the surface of the document sheet 90.

The lens 132 concentrates the light emitted from the main scanningregion A0 in the document sheet 90, onto the light-receiving portion ofthe light amount sensor 133.

The light amount sensor 133 sequentially detects the amount of lightemitted from the main scanning region A0 including a part of the surfaceof the document sheet 90 being relatively moved along the sub scanningdirection D2, thereby to read the image of the document sheet 90sequentially by an amount that corresponds to one line along the mainscanning direction D1.

In the step of reading the image of the document sheet 90, the red lightemitting portion 131R, the green light emitting portion 131G, the bluelight emitting portion 131B are lit in order, and red light, greenlight, and blue light are emitted in order, to the main scanning regionA0. Accordingly, the light amount sensor 133 sequentially outputs threesets of the primary image data Ia respectively representing thedensities of a red image, a green image, and a blue image in the mainscanning region A0. Accordingly, the image of the document sheet 90 canbe read as a color image.

In the case where the image of the document sheet 90 is to be read as amonochrome image, the red light emitting portion 131R, the green lightemitting portion 131G, and the blue light emitting portion 131B are litat the same time, whereby white light is emitted to the main scanningregion A0. Accordingly, the light amount sensor 133 sequentially outputsmonochrome primary image data Ia representing the density of the imagein the main scanning region A0. Accordingly, the image of the documentsheet 90 can be read as a monochrome image. It is also conceivable toobtain the monochrome image as a composite image from a three-colorimage.

The first contact portion 16 a and a color reference portion 14 arearranged so as to be opposed to each other, on the opposite sides of thefirst position P1 in the document sheet conveying path R0. The firstimage sensor 13 a is opposed to the color reference portion 14 via thetransparent first contact portion 16 a. Similarly, the second contactportion 16 b and a color reference portion 14 are arranged so as to beopposed to each other, on the opposite sides of the second position P2in the document sheet conveying path R0. The second image sensor 13 b isopposed to the color reference portion 14 via the transparent secondcontact portion 16 b.

The surface, of each color reference portion 14, that is opposed to itscorresponding one of the first image sensor 13 a and the second imagesensor 13 b is a surface having a uniform reference color and havinghigh light reflectance. In general, the reference color is white. It isalso conceivable that the reference color is a light yellowish color, orthe like.

The image reading device 1 executes an image sensor adjusting step atpredetermined timings. In the image sensor adjusting step, the firstimage sensor 13 a operates when the document sheet 90 is not present atthe first position P1. Further, through comparison between output datafrom the first image sensor 13 a and brightness reference data set inadvance, received-light-amount detection gain of the first image sensor13 a is automatically adjusted.

Similarly, in the image sensor adjusting step, the second image sensor13 b operates when the document sheet 90 is not present at the secondposition P2. Further, through comparison between output data from thesecond image sensor 13 b and the brightness reference data,received-light-amount detection gain of the second image sensor 13 b isautomatically adjusted.

To the first image sensor 13 a and the second image sensor 13 b, avoltage Vi at a predetermined level is applied from a power source 15(see FIG. 4).

<Body Portion of Image Forming Apparatus 10>

The body portion 2 of the image forming apparatus 10 includes deviceswhich form, on a sheet-like recording medium 9, an image correspondingto the image data outputted from each of the first image sensor 13 a andthe second image sensor 13 b. The recording medium 9 is a sheet-likemedium on which an image is to be formed, such as paper, coated paper, apostcard, an envelope, and an OHP sheet, or the like.

The body portion 2 of the image forming apparatus 10 includes a sheetfeeding portion 30, a sheet conveying portion 3, an image formingportion 4, a laser scanning portion 5, a fixing portion 6, and the like.The image forming apparatus 10 shown in FIG. 1 is an image formingapparatus of an electrophotography type. It is also conceivable that theimage forming apparatus 10 is an image forming apparatus of another typesuch as an inkjet type.

The sheet feeding portion 30 is configured to allow a plurality ofrecording media 9 to be placed thereon in a stacked manner. The sheetconveying portion 3 includes a sheet sending-out mechanism 31 and asheet conveying mechanism 32.

The sheet sending-out mechanism 31 includes rollers which rotate incontact with the recording medium 9, and sends out the recording medium9 from the sheet feeding portion 30 toward a sheet conveying path 300.The sheet conveying mechanism 32 conveys the recording medium 9 alongthe sheet conveying path 300. Accordingly, the recording medium 9 passesthough the image forming portion 4 and the fixing portion 6, and then,is discharged through the discharge port of the sheet conveying path300, onto a sheet discharge tray 101.

The image forming portion 4 includes a drum-like photosensitive member41, a charging device 42, a developing device 43, a transfer device 45,a cleaning device 47, and the like. The photosensitive member 41 is oneexample of an image carrier which carries an image of a developer.

The photosensitive member 41 rotates and the charging device 42uniformly charges the surface of the photosensitive member 41. Further,the laser scanning potion 5 performs scanning with laser light, to writean electrostatic latent image on the charged surface of thephotosensitive member 41. Further, the developing device 43 supplies thedeveloper to the photosensitive member 41, to develop the electrostaticlatent image into an image formed with the developer. The developer issupplied from a developer supplying portion not shown, to the developingdevice 43.

Further, the transfer device 45 transfers the image formed with thedeveloper on the surface of the photosensitive member 41, to therecording medium 9 being moved between the photosensitive member 41 andthe transfer device 45. The cleaning device 47 removes the developerremaining on the surface of the photosensitive member 41.

The fixing portion 6 sends out the recording medium 9 on which the imagehas been formed, while nipping the recording medium 9 between a heatingroller 61 having a heater therein and a pressure roller 62. By doingthis, the fixing portion 6 heats the developer on the recording medium 9to fix the image on the recording medium 9.

The operation display portion 80 is an operation input portion includinga touch panel, operation buttons, and the like, for example, and also isa display portion including a liquid crystal display panel, anotification lamp, and the like.

The control portion 8 controls various electric devices included in theimage forming apparatus 10, on the basis of input information inputtedthrough the operation display portion 80 and detection results fromvarious sensors. Further, the control portion 8 also executes imageprocessing on image data outputted from each of the first image sensor13 a and the second image sensor 13 b.

For example, as shown in FIG. 4, the control portion 8 includes an MPU(microprocessor unit) 81, a storage portion 82, a mechanism controlportion 83, an image sensor control portion 84, an image processingportion 85, an AFE (analog front end) 87, and the like. Further, thecontrol portion 8 also includes a laser control portion 86 whichrealizes control functions on the body portion 2 side.

The MPU 81 is a processor which executes various calculation processes.The storage portion 82 is a nonvolatile information storage medium inwhich programs that cause the MPU 81 to execute various processes andother information are stored in advance. The storage portion 82 is aninformation storage medium from which and into which various informationcan be read and written by the MPU 81.

The control portion 8 comprehensively controls the image formingapparatus 10, by the MPU 81 executing various programs stored in advancein the storage portion 82.

The mechanism control portion 83 controls the document sheet sending-outmechanism 122 and the document sheet conveying mechanism 123, and thescanning mechanism 110. For example, when a predetermined first startcondition has been established, the mechanism control portion 83 causesthe document sheet sending-out mechanism 122 and the document sheetconveying mechanism 123 to operate. Accordingly, the document sheet 90is conveyed along the document sheet conveying path R0. When apredetermined second start condition has been established, the mechanismcontrol portion 83 causes the scanning mechanism 110 to operate.Accordingly, the first image sensor 13 a is moved along the sub scanningdirection D2.

For example, the first start condition is that: a predetermined startoperation has been performed on the operation display portion 80 in astate where a sensor not shown has detected that the document sheettable cover 12 had been closed, and that the document sheet 90 had beenset on the document sheet supply tray 121.

The second start condition is that: the start operation has beenperformed on the operation display portion 80 in a state where a sensornot shown has detected that the document sheet table cover 12 had beenclosed, and that the document sheet 90 had not been set on the documentsheet supply tray 121.

The image sensor control portion 84 controls the operation timing of theimage sensor 13. The image sensor control portion 84 includes a lightemission control portion 841 and a data output control portion 842.

The light emission control portion 841 outputs a light emission signalEs at a necessary timing, to each of the red light emitting portion131R, the green light emitting portion 131G, and the blue light emittingportion 131B of the image sensor 13. The light emission control portion841 individually outputs a red light emission signal Es-R which causesthe red light emitting portion 131R to emit light at a desiredbrightness, a green light emission signal Es-G which causes the greenlight emitting portion 131G to emit light at a desired brightness, and ablue light emission signal Es-B which causes the blue light emittingportion 131B to emit light at a desired brightness.

The data output control portion 842 controls the timings of receiving oflight and outputting of the primary image data Ia performed by the lightamount sensor 133. The data output control portion 842 outputs a startpulse signal Sp to the light amount sensor 133 at a necessary timing.

The start pulse signal Sp is a control signal which causes the lightamount sensor 133 to output primary image data Ia that corresponds tothe amount of received light from the immediately preceding output timepoint of the start pulse signal Sp until the current output time pointthereof. The start pulse signal Sp is also a control signal thatinitializes the light amount sensor 133 and that causes the light amountsensor 133 to newly start receiving light. The primary image data Ia istransferred to the AFE 87.

The AFE 87 is circuitry that performs predetermined data processing onthe primary image data Ia outputted from the image sensor 13. The dataprocessing performed by the AFE 87 includes a level shift process foradjusting the offset level of the primary image data Ia, anamplification process for amplifying the primary image data Ia, and anA/D conversion process for converting the analog primary image data Iainto digital secondary image data Id.

That is, the AFE 87 converts primary image partial data Ia1 intosecondary image partial data Id1, converts primary image partial dataIa2 into secondary image partial data Id2, and converts primary imagepartial data Ia3 into secondary image partial data Id3.

In the example shown in FIG. 4, the AFE 87 includes a first AFE 87 a anda second AFE 87 b. The first AFE 87 a converts primary image data Iaoutputted from the first image sensor 13 a into secondary image data Id.The second AFE 87 b converts primary image data Ia outputted from thesecond image sensor 13 b into secondary image data Id.

The image processing portion 85 executes various image processing using,as input data, the secondary image data Id obtained through the AFE 87.For example, the image processing portion 85 executes well-known imageprocessing such as a shading correction process, a process of convertingdata that corresponds to light amount into data that corresponds todensity, gamma correction, and the like.

The laser control portion 86 controls intensity of laser light to beemitted from the laser scanning portion 5, in accordance with densityinformation of each pixel in tertiary image data Idy having beensubjected to image processing performed by the image processing portion85. Accordingly, an electrostatic latent image corresponding to thetertiary image data Idy is formed on the surface of the photosensitivemember 41.

In the present embodiment, the primary image partial data Ia1, Ia2, andIa3, and the secondary image partial data Id1, Id2, and Id3 are examplesof detection data from the single-channel light amount sensors 1331,1332, and 1333, respectively. The secondary image partial data Id1, Id2,and Id3 are detection data outputted through the AFE 87 from thesingle-channel light amount sensors 1331, 1332, and 1333, respectively.

Meanwhile, power consumption of the image sensor 13, which is a CISmodule having a plurality of channels, abruptly and temporarily dropsbefore each single-channel light amount sensor 1331, 1332, 1333 startsoutput of detection data. Thus, depending on the performance of thepower source 15 which supplies power to the image sensor 13, the voltageVi applied to the image sensor 13 temporarily increases before eachsingle-channel light amount sensor 1331, 1332, 1333 starts output ofprimary image data Ia which is detection data. The magnitude of theincrease in the applied voltage Vi is not constant.

FIG. 5 is a time chart of data related to the image sensor 13. FIG. 5shows a case where the image sensor 13 operates in a color mode in whichthe image of the document sheet 90 is read as a color image.

As shown in FIG. 5, in the case where the operation mode of the imagesensor 13 is the color mode, a red light emission signal Es-R, a greenlight emission signal Es-G, and a blue light emission signal Es-B areoutputted in order. Accordingly, the red light emitting portion 131R,the green light emitting portion 131G, and the blue light emittingportion 131B sequentially emit light.

Every time each of the red light emitting portion 131R, the green lightemitting portion 131G, and the blue light emitting portion 131B emitslight, a start pulse signal Sp is outputted. A certain period from theoutput of the start pulse signal Sp is a buffer transfer period tx inwhich the primary image partial data Ia1, Ia2 Ia3 is outputted from thesingle-channel light amount sensor 1331, 1332, 1333 to a buffer notshown. The buffer transfer period tx is a period before thesingle-channel light amount sensor 1331, 1332, 1333 starts externallyoutputting the primary image partial data Ia1, Ia2, Ia3. The buffer ispresent on the data transmission path from the light amount sensor 133to the AFE 87.

As shown in FIG. 5, in the buffer transfer period tx before thesingle-channel light amount sensor 1331, 1332, 1333 starts externallyoutputting the primary image partial data Ia1, Ia2, Ia3, the appliedvoltage Vi from the power source 15 to the image sensor 13 temporarilyincreases. The magnitude of the increase of the applied voltage Vi isnot constant. When the applied voltage Vi varies in this manner, thelevel of the primary image partial data Ia1, Ia2, Ia3 variesirrespective of the detected light amount. Thus, the level of thesecondary image partial data Id1, Id2, Id3 also varies irrespective ofthe detected light amount.

In FIG. 5, ΔL1 and ΔL2 each show the magnitude of variation of thesecondary image partial data Id1, Id2, Id3 caused by various magnitudesof the variation of the applied voltage Vi.

When the level of the secondary image partial data Id1, Id2, Id3 hasvaried irrespective of the detected light amount, a noise image such asa streak extending along the main scanning direction D1 appears in theoutput image, thus causing lowered image quality.

On the other hand, suppressing variation of the applied voltage Vi byemploying a power source 15 that has a high performance of maintainingvoltage leads to increased power source cost.

However, if the image reading device 1 is employed, it is possible toprevent lowering of the image quality of the output image caused byvariation of the applied voltage Vi from the power source 15 to theimage sensor 13, while suppressing cost of the power source 15 for theimage sensor 13. The details will be described below.

[Details of Image Reading Device]

As shown in FIG. 3, the image reading device 1 includes a light-blockingportion 17. The light-blocking portion 17 is a member that blocks lightadvancing toward a reference portion 1331 x of the single-channel lightamount sensor 1331. The reference portion 1331 x is an end portion, ofthe single-channel light amount sensor 1331, which corresponds to an endportion of the main scanning region A0. For example, the referenceportion 1331 x is the photoelectric conversion elements corresponding toa plurality of pixels counted from the extreme end of the single-channellight amount sensor 1331.

That is, the reference portion 1331 x is an end portion of the lightamount sensor 133, and, at the same time, an end portion of thesingle-channel light amount sensor 1331 which is located at the extremeend among the plurality of single-channel light amount sensors 1331,1332, and 1333. In the example shown in FIG. 3, the reference portion1331 x is one of the end portions of the light amount sensor 133.

As shown in FIG. 3, the main scanning region A0 includes a valid mainscanning region A1 corresponding to the maximum width of the documentsheet 90 readable by the image reading device 1, and an invalid mainscanning region A2 which is present outside the valid main scanningregion A1. The reference portion 1331 x is the portion corresponding tothe invalid main scanning region A2.

The light-blocking portion 17 maintains the light receiving environmentfor the reference portion 1331 x at a constant dark state. In this case,data regarding the reference portion 1331 x in the primary image data Iaindicates the minimum level of the amount of light detected by thesingle-channel light amount sensor 1331. The light-blocking portion 17is one example of an environment maintaining portion which maintains thelight receiving environment for the reference portion 1331 x at aconstant state.

As shown in FIG. 6, the image processing portion 85 includes a referencelevel setting portion 851, a correction level calculation portion 852, alevel correction portion 853, a data combining portion 854, and an otherdata processing portion 855. In FIG. 6, the AFE 87 is indicated byvirtual lines (alternate long and two short dashes lines).

The reference level setting portion 851 automatically sets a referencelevel L0 to be used by the correction level calculation portion 852. Thereference level setting portion 851 sets, as the reference level L0, thelevel of detection data regarding the reference portion 1331 x obtainedwhile the light emitting portion 131 is off. The level of the detectiondata is the detection data itself, a representative value of thedetection data, or the like.

For example, the reference level setting portion 851 sets, as thereference level L0, a representative value for data of pixels in thereference portion 1331 x. The representative value is an average value,a minimum value, or the like.

The reference level setting portion 851 executes the process of settingthe reference level L0, when the process of reading the image of thedocument sheet 90 is not performed. For example, when a sensor not shownhas detected that the document sheet table cover 12 had been closed, orthat the document sheet 90 had been placed on the document sheet supplytray 121, the reference level setting portion 851 executes the processof setting the reference level L0. It is also conceivable that thereference level setting portion 851 executes the process of setting thereference level L0 immediately before the start of the process ofreading the image of the document sheet 90.

The correction level calculation portion 852 calculates a deviation ΔLxbetween the reference level L0 set in advance and the level of detectiondata regarding the reference portion 1331 x obtained when the process ofreading the image of the document sheet 90 is performed. The correctionlevel calculation portion 852 calculates the deviation ΔLx, each timethe light amount sensor 133 outputs primary image data Ia thatcorresponds to the main scanning region A0.

The level correction portion 853 corrects the level of each of thesecondary image partial data Id1, Id2, and Id3 from all the respectivesingle-channel light amount sensors 1331, 1332, and 1333, in accordancewith the deviation ΔLx. At that time, the level correction portion 853performs the correction by shifting the level of each of the secondaryimage partial data Id1, Id2, and Id3 such that the deviation ΔLx becomes0.

Each time the light amount sensor 133 outputs primary image data Ia thatcorresponds to the main scanning region A0, the level correction portion853 corrects the level of each of the secondary image partial data Id1,Id2, and Id3 from all the respective single-channel light amount sensors1331, 1332, and 1333, in accordance with the latest deviation ΔLx.

Therefore, in the case where the image sensor 13 operates in the colormode, the level correction portion 853 corrects, for each color of lightemitted from the light emitting portion 131, the level of each of thesecondary image partial data Id1, Id2, and Id3 from all the respectivesingle-channel light amount sensors 1331, 1332, and 1333, in accordancewith the deviation ΔLx.

As described above, in the color mode, the red light emitting portion131R, the green light emitting portion 131G, and the blue light emittingportion 131B sequentially emit light, and the single-channel lightamount sensors 1331, 1332, and 1333 respectively output primary imagepartial data Ia1, Ia2, and Ia3 for each emitted light color.

Meanwhile, in the monochrome mode in which the image of the documentsheet 90 is read as a monochrome image, the entirety of the lightemitting portion 131 emits light. Further, the single-channel lightamount sensors 1331, 1332, and 1333 sequentially output primary imagepartial data Ia1, Ia2, and Ia3, respectively, in a cycle set in advance.

Therefore, in the monochrome mode, every time each single-channel lightamount sensor 1331, 1332, 1333 outputs primary image partial data Ia1,Ia2, Ia3 cyclically while the light emitting portion 131 is emittinglight, the level correction portion 853 corrects the level of secondaryimage partial data Id1, Id2, Id3.

The magnitudes of the variations of the primary image partial data Ia1,Ia2, and Ia3 caused by various magnitudes of the variation of theapplied voltage Vi are substantially the same among the primary imagepartial data Ia1, Ia2, and Ia3 which are outputted at the same time,respectively. In other words, the magnitudes of the variations of thesecondary image partial data Id1, Id2, and Id3 are substantially thesame among the secondary image partial data Id1, Id2, and Id3 which areoutputted at the same time.

Therefore, if the level of each of the secondary image partial data Id1,Id2, and Id3 from all the respective single-channel light amount sensors1331, 1332, and 1333 is corrected by using the deviation ΔLx obtainedfrom detection data from one single-channel light amount sensor 1331,errors caused by variation of the applied voltage Vi are removed fromall the secondary image partial data Id1, Id2, and Id3.

The data combining portion 854 generates image data of the entirety ofthe valid main scanning region A1 by combining the corrected secondaryimage partial data Id1, Id2, and Id3. At that time, the data combiningportion 854 generates image data of the entirety of the valid mainscanning region A1 by removing data of the invalid main scanning regionA2.

The other data processing portion 855 executes image processing such asa well-known shading correction process, a process of converting datathat corresponds to light amount into data that corresponds to density,and the like, and outputs tertiary image data Idy having been processed.Then, the image forming portion 4 forms on the recording medium 9 animage that corresponds to the tertiary image data Idy obtained by theimage reading device 1. The tertiary image data Idy is the detectiondata from the light amount sensor 133 having been corrected by thecorrection level calculation portion 852 and the level correctionportion 853.

As described above, if the image reading device 1 is employed, even whenthe voltage maintaining performance of the power source 15 is not sohigh, it is possible to prevent lowering of the image quality of theoutput image caused by variation of the applied voltage Vi from thepower source 15 to the image sensor 13. Therefore, cost of the powersource 15 can be suppressed.

In addition, since the light-blocking portion 17 is employed as a memberthat maintains the light receiving environment for the reference portion1331 x at a dark state, the level of the detection data regarding thereference portion 1331 x obtained while the light emitting portion 131is off can be used as the reference level L0. This facilitates settingof the reference level L0.

In the color mode, the magnitude of variation of the applied voltage Vidiffers for each color of light emitted from the light emitting portion131. Thus, it is effective that data corrections by the correction levelcalculation portion 852 and by the level correction portion 853 areperformed each time the color of light emitted from the light emittingportion 131 is switched.

Application Example

In the image reading device 1, it is also conceivable that a referencecolor member having a surface of black or another color formed thereonis used instead of the light-blocking portion 17. In this case, thereference color member is disposed at a position opposed to thereference portion 1331 x of the single-channel light amount sensor 1331.The reference color member is one example of the environment maintainingportion.

It is also conceivable that, in the image reading device 1, the AFE 87executes, instead of the image processing portion 85, the processesperformed by the correction level calculation portion 852 and by thelevel correction portion 853. In this case, the AFE 87 performs the sameprocesses as the processes performed by the correction level calculationportion 852 and the level correction portion 853, on the primary imagepartial data Ia1, Ia2, and Ia3.

It is also conceivable that, in the image processing portion 85, thecorrection level calculation portion 852 and the level correctionportion 853 execute a correction process on the image data obtainedthrough the combining performed by the data combining portion 854.

The image reading device and the image forming apparatus according tothe present disclosure can be configured by freely combining theembodiment and the application example described above, or modifying orpartially omitting the embodiment and the application example asappropriate, within the scope of the disclosure recited in each claim.

It is to be understood that the embodiments herein are illustrative andnot restrictive, since the scope of the disclosure is defined by theappended claims rather than by the description preceding them, and allchanges that fall within metes and bounds of the claims, or equivalenceof such metes and bounds thereof are therefore intended to be embracedby the claims.

The invention claimed is:
 1. An image reading device comprising: animage sensor module including: a light emitting portion configured toemit light to a main scanning region extending along one straight line;and a plurality of single-channel light amount sensors configured toperform in parallel receiving light from corresponding partial scanningregions which are each a part of the main scanning region, andoutputting detection data of an amount of the received light; anenvironment maintaining portion configured to maintain, at a constantstate, a light receiving environment for a reference portion forming anend portion of a single-channel light amount sensor which corresponds toan end portion of the main scanning region; and a level correctionportion configured to correct, each time the image sensor module outputsthe detection data that corresponds to the main scanning region, a levelof detection data newly obtained from each of all the single-channellight amount sensors in accordance with a deviation between a level ofnewly obtained detection data regarding the reference portion and areference level set in advance, wherein the environment maintainingportion is a light-blocking portion configured to block light advancingtoward the reference portion; and the plurality of single-channel lightamount sensors are disposed in series along the one straight linewithout overlapping each other.
 2. The image reading device according toclaim 1, further comprising a reference level setting portion configuredto set, as the reference level, the level of the detection dataregarding the reference portion obtained while the light emittingportion is off.
 3. The image reading device according to claim 1,wherein the image sensor module includes a plurality of the lightemitting portions respectively having different emitted light colors andrespectively being capable of emit light individually, and when thelight emitting portions sequentially emit light and each of thesingle-channel light amount sensors outputs the detection data for eachemitted light color, the level correction portion corrects the level ofthe detection data from each of all the single-channel light amountsensors in accordance with the deviation between the level of thedetection data regarding the reference portion and the reference level,for each emitted light color.
 4. An image forming apparatus comprising:the image reading device according to claim 1; and an image formingportion configured to form, on a recording medium, an image thatcorresponds to the detection data having been corrected, the detectiondata being obtained by the image reading device.